In recent years, progresses for laser light sources are remarkable. Previously an expensive large-size apparatus was needed for a laser. Presently, in contrast, laser light sources can be obtained using an inexpensive small-size apparatus, and the thus-obtained laser light sources are stable. This has been brought about by active and steady development of the semiconductor laser for DVDs and so on in the electronics industry. A laser of shorter wavelength has been developed for recording a high density of information, resulting in laser light sources for a variety of wavelength ranging from short to long.
Description of blue semiconductor laser light sources was presented by NICHIA CORPORATION in the 48th Meeting of the Japan Society of Applied Physics and Related Societies in March in 2001.
On the other hand, digitalization has been remarkably widespread in the field of color prints using color photographic printing paper. For example, a digital exposure system that uses laser scanning exposure has spread rapidly, compared with an ordinary analog exposure system in which printing is directly conducted from a processed color negative film using a color printer.
Such a digital exposure system is characterized in that high image quality is obtained by image processing, and it greatly contributes to improving qualities of color prints using color photographic printing paper. Further, according to the rapid spread of digital cameras, it is also an important factor that a color print with high image quality is easily obtained from these electronic recording media. It is believed that they will rapidly spread further. A digital exposure system, and an image-forming method using the same are described in detail in JP-A-11-84284 (“JP-A” means unexamined published Japanese patent application) and JP-A-2001-75219.
From the above-described situation, there is a demand for actualization of a color print system that attains low cost and high quality though a combination of inexpensive laser light sources and a digital exposure system. However, inexpensive laser light sources and the color print system do not always accord with each other. In development of the semiconductor laser, the laser wavelength is made shorter moment by moment for recording a high density of information. Accordingly, it is believed that an inexpensive semiconductor laser will shift to a shorter wavelength direction from now on, from the point of productivity. If the wavelength of the spectral sensitivity maximum of a color photographic printing paper is changed in accordance with laser light sources, a problem arises that interchangeability of the digital exposure system and the analogue exposure system is deteriorated. Even if the wavelength of the spectral sensitivity maximum of a color photographic printing paper is arranged in accordance with a wavelength of the laser light sources that is available at the present time neglecting interchangeability, it is not actual policy to adapt to the situation in which the wavelength of the laser light sources always varies moment by moment. Therefore, such color photographic printing paper cannot be put into practical use. Like this, an image-forming method and a development of a light-sensitive material not being subjected to fluctuation in exposure wavelength are strongly desired.
Generally, there is also a best exposure wavelength suitable for a color photographic printing paper. Hitherto, generally a wavelength near the wavelength of spectral sensitivity maximum has been chosen. This is because a photographic sensitivity is reduced if a color photographic printing paper is exposed to light having a wavelength different from the wavelength of spectral sensitivity maximum.
Surprisingly, such exposure caused a further serious problem. Namely, it was found that sensitiveness to fluctuation in exposure environments (particularly temperature fluctuation) became more remarkable. In other words, if the color photographic printing paper is exposed to light having a wavelength different from the wavelength of spectral sensitivity maximum, photographic sensitivity is changed depending on the environmental temperature at the time of exposure, and an image of constant quality cannot be obtained. The reduction in sensitivity can be prevented by increasing both the exposure amount and exposure power. However, it was difficult to substantially reduce the sensitivity fluctuation owing to changes of exposure environments.
JP-A-2001-75219 discloses the relation of a wavelength of the spectral sensitivity maximum and a wavelength of the exposure light sources. However, the wavelength of the exposure light sources disclosed therein is in the wavelength of spectral sensitivity maximum. Therefore, the above-mentioned publication completely fails to disclose the present invention. The above-mentioned JP-A-2001-75219 proposes a means to enhance the maximum density that can be obtained by a light-sensitive material employing a high silver chloride emulsion. However, the publication provides no specific solution of the above-mentioned problem. In addition, the exposure wavelength is set in a wavelength range at which a light-sensitive layer of the light-sensitive material has the spectral sensitivity maximum. Therefore, the above-mentioned publication completely fails to disclose the present invention.
Meanwhile, as to the color print processes, such technologies as an ink jet method, a sublimation-type method, and a color xerography have each made a progress to an extent that these methods are reputed for their photographic qualities and these are being accepted as color print processes. Among these processes, the features of the digital exposure process using color print paper reside in high-quality images, high productivity, and excellent colorfastness of images. Based on these features, it is required to provide photographs having further higher qualities in a simpler and less expensive measures.
In the color print process comprising laser exposure of color print paper, a digital scanning exposure system, which uses a monochromatic high-density light such as a gas laser, a semiconductor laser, or a second harmonic generation (SHG) light source comprising a combination of a semiconductor laser as an exciting light source and a nonlinear optical crystal, is actually used. The exposing apparatus using a gas laser is of a large size and therefore a large space is necessary for the accommodation. Presently, examples of the exposing apparatus using a gas laser as the light source include Lambda (trade name) series manufactured by Durst Corporation. However, the apparatus is large in size and the use is limited to a special application such as large-enlargement prints and the apparatus is not used for so-called amateur prints.
On the other hand, since an exposing apparatus using a semiconductor laser is far smaller than an exposing apparatus using a gas laser, the exposing apparatus using a semiconductor laser is suitable for a mini-lab which produces color prints in the area around a shop counter. Actually, an example of the exposing apparatus for a mini-lab is developed as a Frontier (trade name) series manufactured by Fuji Photo Film Co., Ltd. and this apparatus uses a semiconductor laser. When a color print is produced by the printing on a color print paper by laser exposure, normally blue light, green light, and red light are used as laser lights. This is because the wavelengths of these laser lights are close to the exposure wavelengths for color print paper for conventional analog type exposure and therefore the merit is that the main color print paper production technique can be used commonly with that for analog exposure and digital exposure. Because of the absence of a semiconductor laser, which fulfills such requirements as life and exposure intensity in the blue and green wavelength regions, blue and green laser lights are obtained by use of a second harmonic generation (SHG) light source comprising a combination of a red or infrared semiconductor laser as an exciting light source and a nonlinear optical crystal. The use of a nonlinear optical crystal causes a limitation in making the apparatus compact and inexpensive. This presents a problem particularly in an amateur market where cost is important.
As presented by NICHIA CORPORATION in the 48th Meeting of the Japan Society of Applied Physics and Related Societies in March in 2001, in recent years a blue semiconductor laser having wavelengths of 430 to 450 nm has reached the level enabling its actual use. The use of this semiconductor laser makes it possible to obtain a blue laser without the use of a nonlinear optical crystal.
However, in the image obtained by using as a light source a blue semiconductor laser whose wavelength is shorter than 450 nm, problems that color purity of yellow decreased and tints changed in the peripheral region of prints occurred. The problem that color purity of yellow decreased was alleviated by the sensitivity adjustment of a blue-sensitive emulsion but the problem that tints changed in the peripheral region of prints was not alleviated. Although the problem of tint change in the peripheral region of prints was alleviated by the gradation adjustment of a blue-sensitive emulsion, the gradation adjustment of a blue-sensitive emulsion led to the problem that color purity of yellow further decreased.
In recent years, high quality photographic light-sensitive materials which make it possible to outstandingly shorten the time required for an image forming process from an exposure step to a drying step through some treating steps have been desired as a part of improvements in a service to customers and as a measures for improving productivity in the photograph treatment service industry. In order to cope with this desire, for example, an exposure treatment system are being put to the market from each company in which system, the process since the exposure step is started until the drying step is finished is rapidly carried out in a total time about 4 minutes by shortening the time required from the exposure to the treatment (called latent image time in the field concerned) to about 10 seconds and carrying out the subsequent color developing treatment for 45 seconds (for example, in Frontier 350 manufactured by Fuji Photo Film Co., Ltd.). As to an exposure treatment using these systems, continuous exposure treatment is carried out in each processing laboratory, and the developed products are conveyed to photo processing shops and delivered to customers. However, a simple exposure treating system is being installed inside of a photo processing shop and the shop offers its service to return a photographic image to customers in about one hour from reception in these days. These systems are superior in shortening the time required until a photographic image is returned to customers. If there is a system capable of completing a process from the exposure to the treatment in 1 to 2 minutes by further shortening the latent image time, the time required for reception to return of photograph is greatly shortened and it is therefore expected to contribute to a much improvement in service.
It has been found that in case of conducting such super-rapid processing under the conditions, if a silver halide particle is small-sized from the necessity of improving developing progress and the amount of a spectral sensitizing dye is increased to obtain high sensitivity, the problem of residual color caused by a sensitizing dye remaining in a dried film is enhanced after treatment. Particularly residual color in a blue-sensitive layer to be formed by application as the lowermost layer of an image forming coating film is increased. As a measures used to solve this problem, technologies concerning a silver halide photographic light-sensitive material using a sensitizing dye that has as a substituent, an aromatic group having a specific structure differing from a phenyl group are disclosed in JP-A-6-230501. These technologies are however found to be quite unsatisfactory to achieve super-rapid processing in which the time from start of developing step to finish of drying step is a little more than one minute. Moreover, residual color improving technologies using a water-soluble diaminostilbene type fluorescent whiting agent or a highly hydrophilic sensitizing dye as described in JP-A-6-329936 and a method for promoting the washing of a sensitizing dye by decreasing not only the thickness of a swelled film but also the thickness of a dry film are keenly studied. However, these technologies are not satisfactory yet and it is therefore desired to develop technologies for improving problem of residual color.
Also, a system performing exposure using laser light is introduced to the market to make it possible to return a high quality print to customers by taking in information from a negative image obtained by taking a photograph and performing image treatment. This system is outstandingly spread at a high rate because of the important feature that high image quality is obtained and a color print having high image quality is obtained easily from an image recording medium of a digital camera or the like according to this system. In such a system, exposure is carried out using a laser and therefore exposure illuminance is made high, so that it is required for a silver halide light-sensitive material to have very superb characteristics coping with high illuminance. A method in which a silver halide is doped with a metal complex to thereby improve the reciprocity characteristics at a high illuminance, thereby making exposure illuminance conversion to coordinate a gradation at a middle to low illuminance and a gradation at high illuminance has been used from of old. However, this method has the drawback that the latent image time becomes long and it is therefore desired to develop technologies for more shortening the latent image time for laser exposure.